Hydraulic Based Efficient Energy Storage And Regeneration System

ABSTRACT

An energy storage and regeneration system that converts irregular, non-constant, and variable input power to regular, constant, and controlled output power using hydraulics whereby the irregular input power is used to pump hydraulic fluid into an accumulator array where it is stored pressurized. Energy is released in a controlled fashion using a hydraulic motor operated by the pressurized hydraulic fluid from the accumulator array, in accordance with the specified power demand. One or more power units may be deployed depending on the amount of energy required at the output. Each power unit includes a hydraulic motor and associated floating accumulator whose internal pressure is controlled to maintain a substantially constant pressure differential across its associated motor.

REFERENCE TO PRIORITY APPLICATIONS

This application is a continuation in part of U.S. application Ser. No. 13/641,277, filed Nov. 29, 2012, entitled “Hydraulic Power Converter,” which is a 371 of PCT/IB2011/051831, filed Apr. 27, 2011, entitled “Hydraulic Power Converter,” which claims priority to U.S. Provisional Application Ser. No. 61/328,746, filed Apr. 28, 2010, entitled “Novel System for Efficient Improvement in Hybrid Vehicles,” all of which are incorporated herein by reference in their entirety.

FIELD OF THE DISCLOSURE

The subject matter disclosed herein relates to the field of hydraulics and more particularly relates to an efficient system for storing and regenerating energy using hydraulics.

BACKGROUND OF THE INVENTION

Currently, the world is witnessing huge growth and development of renewable energy sources such as wind power, solar photovoltaics (PV) and thermal power, hydropower, wave and tidal power, etc. Along with the growth of renewable energy sources is the problem of matching energy generation with energy consumption and demand. For example, wind turbines only generate power when the wind is sufficiently strong. PV solar arrays only generate power when the sun is shining.

Peaks in energy demand, on the other hand, are not necessarily correlated with peaks in energy generation. In recent years, there have been efforts made to manage the electricity supply. The problem of efficiently handling irregular and non-constant energy supplies and variable demand for electricity still remains unsolved. For example, solar plants supply energy only during sunny days, and wind turbines supply power only when it is windy. Electricity demand is characterized by a peak, that requires more power stations to be built to supply the peak demand than necessary to supply the average demand.

There is thus a need to both harness the irregular power generated by renewable sources as well as to efficiently meet the energy demands of end users over time.

SUMMARY OF THE INVENTION

The present invention is a hydraulics based energy storage and regeneration system. The system is operative to convert irregular, non-constant, and variable input power to regular, constant, and controlled output power using hydraulics whereby the irregular input power is used to pump hydraulic fluid into an accumulator array where it is stored pressurized. Energy is released in a controlled fashion using a hydraulic motor operated by the pressurized hydraulic fluid from the accumulator array, in accordance with the specified power demand. One or more power units may be deployed depending on the amount of energy required at the output. Each power unit includes a hydraulic motor and associated floating accumulator whose internal pressure is controlled to maintain a substantially constant pressure differential across its associated motor thereby providing steady output power. The operation of the system can be controlled electrically and mechanically, and can be integrated into various energy system sources including renewable energy such as wind and PV or thermal solar.

This, additional, and/or other aspects and/or advantages of the embodiments of the present invention are set forth in the detailed description which follows; possibly inferable from the detailed description; and/or learnable by practice of the embodiments of the present invention.

There is thus provided in accordance with the invention, an apparatus for storing and regenerating energy, comprising a hydraulic pump coupled to a source of mechanical energy providing variable, non-constant input power, the hydraulic pump operative to convert the mechanical energy to hydraulic energy at its output, an accumulator array including a plurality of N accumulator tanks, the accumulator array coupled to the output of the hydraulic pump, the accumulator array operative to store the hydraulic energy generated by the hydraulic pump in one or more accumulator tanks, one or more power units coupled to the accumulator array and operative to convert hydraulic energy released from the accumulator array into mechanical energy, and a control system coupled to the accumulator array and the one or more power units, the control system operative to coordinate the storage and release of hydraulic energy into and out of the N individual accumulator tanks of the accumulator array in accordance with an external power demand such that the variable, non-constant input power is converted into relatively steady, constant power output by the one or more power units.

There is also provided in accordance with the invention, a method of storing and regenerating energy, the method comprising receiving variable, non-constant input power from an energy source, converting the input power to hydraulic energy, storing the hydraulic energy generated in a plurality of N accumulator tanks making up an accumulator array, releasing stored hydraulic energy from the accumulator array in a controlled manner to power one or more power units, converting, at each power unit, hydraulic energy released from the accumulator array into mechanical energy, and coordinating, via a control system, the storage and release of hydraulic energy into and out of the N individual accumulator tanks of the accumulator array in accordance with an external power demand such that the variable, non-constant input power is converted into relatively steady, constant power output by the one or more power units.

There is further provided in accordance with the invention, an apparatus for storing and regenerating energy, comprising a hydraulic pump coupled to a source of mechanical energy providing variable, non-constant input power, the hydraulic pump operative to convert the mechanical energy to hydraulic energy at its output, an accumulator array including a plurality of N accumulator tanks, the accumulator array coupled to the output of the hydraulic pump, the accumulator array operative to store the hydraulic energy generated by the hydraulic pump in one or more accumulator tanks, one or more power units coupled to the accumulator array and operative to convert hydraulic energy released from the accumulator array into mechanical energy, each power unit including a hydraulic motor and a floating accumulator, a control system coupled to the accumulator array and the one or more power units, the control system operative to coordinate the storage and release of hydraulic energy into and out of the N individual accumulator tanks of the accumulator array and the floating accumulator in each power unit in accordance with an external power demand such that the variable, non-constant input power is converted into relatively steady, constant power output by the one or more power units, and wherein the control system is operative to control the charging and discharging of pressurized hydraulic fluid into and out of the floating accumulator in each respective power unit such that the pressure differential across a power unit's corresponding hydraulic motor is maintained substantially constant.

There is also provided in accordance with the invention, a method of storing and regenerating energy, the method comprising receiving variable, non-constant input power from an energy source, converting, via a hydraulic pump, the input power to hydraulic energy, storing the hydraulic energy generated in an accumulator array, releasing stored hydraulic energy from the accumulator array in a controlled manner to power one or more power units, converting, via a hydraulic motor in each power unit, hydraulic energy released from the accumulator array into a relatively steady source of mechanical energy, providing a floating accumulator in each power unit coupled to a respective hydraulic motor, coordinating, via a control system, the storage and release of hydraulic energy into and out of the accumulator array and the floating accumulator in each power unit in accordance with an external power demand such that the variable, non-constant input power is converted into relatively steady, constant power output by the one or more power units, and control, via the control system, the charging and discharging of pressurized hydraulic fluid into and out of the floating accumulator in each respective power unit so as to maintain a substantially constant pressure differential across a power unit's respective hydraulic motor.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is explained in further detail in the following exemplary embodiments and with reference to the figures, where identical or similar elements may be partly indicated by the same or similar reference numerals, and the features of various exemplary embodiments being combinable. The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

FIG. 1 is a block diagram illustrating an example computer processing system adapted to implement the control system portion of the present invention;

FIG. 2 is a diagram illustrating an example prior art accumulator in an empty state;

FIG. 3 is a diagram illustrating an example prior art accumulator in a full state;

FIG. 4 is a block diagram illustrating a first example embodiment of the energy storage and regeneration system of the present invention;

FIG. 5 is a block diagram illustrating a second example embodiment of the energy storage and regeneration system of the present invention;

FIG. 6 is a block diagram illustrating a third example embodiment of the energy storage and regeneration system of the present invention;

FIG. 7 is a diagram illustrating an example accumulator array in more detail;

FIGS. 8A and 8B are a block diagram illustrating a fourth example embodiment of the energy storage and regeneration system of the present invention;

FIGS. 9A and 9B are a block diagram illustrating a fifth example embodiment of the energy storage and regeneration system of the present invention;

FIG. 10 is a diagram illustrating an example control system of the present invention in more detail;

FIG. 11 is a flow diagram illustrating an example method of generating and storing hydraulic energy; and

FIG. 12 is a flow diagram illustrating an example method of generating steady electric/mechanical energy from stored hydraulic energy.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be understood by those skilled in the art, however, that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying figures. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various forms. In addition, each of the examples given in connection with the various embodiments of the invention which are intended to be illustrative, and not restrictive.

The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings.

The figures constitute a part of this specification and include illustrative embodiments of the present invention and illustrate various objects and features thereof. Further, the figures are not necessarily to scale, some features may be exaggerated to show details of particular components. In addition, any measurements, specifications and the like shown in the figures are intended to be illustrative, and not restrictive. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

Because the illustrated embodiments of the present invention may for the most part, be implemented using electronic components and circuits known to those skilled in the art, details will not be explained in any greater extent than that considered necessary, for the understanding and appreciation of the underlying concepts of the present invention and in order not to obfuscate or distract from the teachings of the present invention.

Any reference in the specification to a method should be applied mutatis mutandis to a system capable of executing the method. Any reference in the specification to a system should be applied mutatis mutandis to a method that may be executed by the system.

Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrases “in one embodiment,” “in an example embodiment,” and “in some embodiments” as used herein do not necessarily refer to the same embodiment(s), though it may. Furthermore, the phrases “in another embodiment,” “in an alternative embodiment,” and “in some other embodiments” as used herein do not necessarily refer to a different embodiment, although it may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.

In addition, as used herein, the term “or” is an inclusive “or” operator, and is equivalent to the term “and/or,” unless the context clearly dictates otherwise. The term “based on” is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of “a,” “an,” and “the” include plural references. The meaning of “in” includes “in” and “on.”

As will be appreciated by one skilled in the art, the present invention may be embodied as a system, method, computer program product or any combination thereof. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, the present invention may take the form of a computer program product embodied in any tangible medium of expression having computer usable program code embodied in the medium.

The invention may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The invention may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.

Any combination of one or more computer usable or computer readable medium(s) may be utilized. The computer-usable or computer-readable medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CDROM), an optical storage device, a transmission media such as those supporting the Internet or an intranet, or a magnetic storage device. Note that the computer-usable or computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory. In the context of this document, a computer-usable or computer-readable medium may be any medium that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device.

Computer program code for carrying out operations of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++, C# or the like, conventional procedural programming languages, such as the “C” programming language, and functional programming languages such as Prolog and Lisp, machine code, assembler or any other suitable programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network using any type of network protocol, including for example a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

The present invention is described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented or supported by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

The invention is operational with numerous general purpose or special purpose computing system environments or configurations. Examples of well-known computing systems, environments, and/or configurations that may be suitable for use with the invention include, but are not limited to, personal computers, server computers, cloud computing, hand-held or laptop devices, multiprocessor systems, microprocessor, microcontroller or microcomputer based systems, set top boxes, programmable consumer electronics, ASIC or FPGA core, DSP core, network PCs, minicomputers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like.

In addition, the invention is operational in systems incorporating sensors such as found in automated factories, in mobile devices such as tablets and smartphones, smart meters installed in the power grid and control systems for robot networks. In general, any computation device that can host an agent can be used to implement the present invention.

A block diagram illustrating an example computer processing system adapted to implement the control system portion of the present invention is shown in FIG. 1. The exemplary computer processing system, generally referenced 10, for implementing the invention comprises a general purpose computing device 11. Computing device 11 comprises central processing unit (CPU) 12, host/PIC/cache bridge 20 and main memory 24.

The CPU 12 comprises one or more general purpose CPU cores 14 and optionally one or more special purpose cores 16 (e.g., DSP core, floating point, etc.). The one or more general purpose cores execute general purpose opcodes while the special purpose cores execute functions specific to their purpose. The CPU 12 is coupled through the CPU local bus 18 to a host/PCI/cache bridge or chipset 20. A second level (i.e. L2) cache memory (not shown) may be coupled to a cache controller in the chipset. For some processors, the external cache may comprise an L1 or first level cache. The bridge or chipset 20 couples to main memory 24 via memory bus 20. The main memory comprises dynamic random access memory (DRAM) or extended data out (EDO) memory, or other types of memory such as ROM, static RAM, flash, and non-volatile static random access memory (NVSRAM), bubble memory, etc.

The computing device 11 also comprises various system components coupled to the CPU via system bus 26 (e.g., PCI). The host/PCI/cache bridge or chipset 20 interfaces to the system bus 26, such as peripheral component interconnect (PCI) bus. The system bus 26 may comprise any of several types of well-known bus structures using any of a variety of bus architectures. Example architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Associate (VESA) local bus and Peripheral Component Interconnect (PCI) also known as Mezzanine bus.

Various components connected to the system bus include, but are not limited to, non-volatile memory (e.g., disk based data storage) 28, video/graphics adapter 30 connected to display 32, user input interface (I/F) controller 31 connected to one or more input devices such mouse 34, tablet 35, microphone 36, keyboard 38 and modem 40, network interface controller 42, peripheral interface controller 52 connected to one or more external peripherals such as printer 54 and speakers 56. The network interface controller 42 is coupled to one or more devices, such as data storage 46, remote computer 48 running one or more remote applications 50, via a network 44 which may comprise the Internet cloud, a local area network (LAN), wide area network (WAN), storage area network (SAN), etc. A small computer systems interface (SCSI) adapter (not shown) may also be coupled to the system bus. The SCSI adapter can couple to various SCSI devices such as a CD-ROM drive, tape drive, etc.

The non-volatile memory 28 may include various removable/non-removable, volatile/nonvolatile computer storage media, such as hard disk drives that reads from or writes to non-removable, nonvolatile magnetic media, a magnetic disk drive that reads from or writes to a removable, nonvolatile magnetic disk, an optical disk drive that reads from or writes to a removable, nonvolatile optical disk such as a CD ROM or other optical media. Other removable/non-removable, volatile/nonvolatile computer storage media that can be used in the exemplary operating environment include, but are not limited to, magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like.

A user may enter commands and information into the computer through input devices connected to the user input interface 31. Examples of input devices include a keyboard and pointing device, mouse, trackball or touch pad. Other input devices may include a microphone, joystick, game pad, satellite dish, scanner, etc.

The computer 11 may operate in a networked environment via connections to one or more remote computers, such as a remote computer 48. The remote computer may comprise a personal computer (PC), server, router, network PC, peer device or other common network node, and typically includes many or all of the elements described supra. Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet.

When used in a LAN networking environment, the computer 11 is connected to the LAN 44 via network interface 42. When used in a WAN networking environment, the computer 11 includes a modem 40 or other means for establishing communications over the WAN, such as the Internet. The modem 40, which may be internal or external, is connected to the system bus 26 via user input interface 31, or other appropriate mechanism.

The computing system environment, generally referenced 10, is an example of a suitable computing environment and is not intended to suggest any limitation as to the scope of use or functionality of the invention. Neither should the computing environment be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary operating environment.

In one embodiment, the software adapted to implement the system and methods of the present invention can also reside in the cloud. Cloud computing provides computation, software, data access and storage services that do not require end-user knowledge of the physical location and configuration of the system that delivers the services. Cloud computing encompasses any subscription-based or pay-per-use service and typically involves provisioning of dynamically scalable and often virtualized resources. Cloud computing providers deliver applications via the internet, which can be accessed from a web browser, while the business software and data are stored on servers at a remote location.

In another embodiment, software adapted to implement the system and methods of the present invention is adapted to reside on a computer readable medium. Computer readable media can be any available media that can be accessed by the computer and capable of storing for later reading by a computer a computer program implementing the method of this invention. Computer readable media includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media. Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer. Communication media typically embodies computer readable instructions, data structures, program modules or other data such as a magnetic disk within a disk drive unit. The software adapted to implement the system and methods of the present invention may also reside, in whole or in part, in the static or dynamic main memories or in firmware within the processor of the computer system (i.e. within microcontroller, microprocessor or microcomputer internal memory).

Other digital computer system configurations can also be employed to implement the system and methods of the present invention, and to the extent that a particular system configuration is capable of implementing the system and methods of this invention, it is equivalent to the representative digital computer system of FIG. 1 and within the spirit and scope of this invention.

Once they are programmed to perform particular functions pursuant to instructions from program software that implements the system and methods of this invention, such digital computer systems in effect become special purpose computers particular to the method of this invention. The techniques necessary for this are well-known to those skilled in the art of computer systems.

It is noted that computer programs implementing the system and methods of this invention will commonly be distributed to users on a distribution medium such as floppy disk, CDROM, DVD, flash memory, portable hard disk drive, etc. From there, they will often be copied to a hard disk or a similar intermediate storage medium. When the programs are to be run, they will be loaded either from their distribution medium or their intermediate storage medium into the execution memory of the computer, configuring the computer to act in accordance with the method of this invention. All these operations are well-known to those skilled in the art of computer systems.

The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or by combinations of special purpose hardware and computer instructions.

A diagram illustrating an example prior art accumulator in an empty state is shown in FIG. 2. A diagram illustrating an example prior art accumulator in a full state is shown in FIG. 3. The accumulator, generally referenced 60, comprises a tank 62 constructed from a suitable material, e.g., steel, to contain high pressures, a piston 68, a bladder 74 containing a gas such as nitrogen 64 and opening 70. In operation, pressurized oil 66, i.e. hydraulic fluid, is pumped into the accumulator through opening 72 and pushes against the piston 68. Due to the pressure, the piston moves to compress the gas bladder 74. Since gas is compressible, the bladder is compressed to a smaller and smaller size as more and more pressured oil is pumped into the accumulator.

FIG. 2 shows the accumulator in a near empty state. The gas bladder 74 is expanded to comprise the majority of the internal space. FIG. 3 shows the accumulator in an almost full state where the gas bladder 74 is compressed to occupy a small portion of the internal space. In this state, the majority of the internal space is taken up by the oil 66. Thus, the bladder 74 of gas 64 expands in accordance with pressurized oil entering the accumulator as well as contracts as pressurized oil is released from the accumulator.

A block diagram illustrating a first example embodiment of the energy storage and regeneration system of the present invention is shown in FIG. 4. The energy storage and regeneration system (ESRS), generally referenced 80, comprises a hydraulic pump 86 coupled to a source of energy 84, accumulator array 88, hydraulic motor 90 coupled to a load 92, hydraulic fluid reservoir 94, and control system 82.

In operation, the ESRS 80 receives variable, irregular, discontinuous power from an energy source 84 and delivers controlled, constant power to a load 92. The hydraulic pump 86 is configured to receive the irregular power from source 84 and use it to pump hydraulic fluid from the reservoir 94 to the accumulator array 88. The accumulator array comprises a plurality of accumulator tanks such as shown in FIGS. 1 and 2 connected in tandem where each individual accumulator is configured to receive, store and supply hydraulic pressure independently of the other accumulators, i.e. each accumulator can be pressurized to different pressure levels. Thus, each accumulator tank can operate independently and in an isolated manner from all the other accumulator tanks.

Pressurized oil stored in the accumulator array is released to power the hydraulic motor 90. The motor can supply mechanical energy to the load 92 which may comprise an electric generator or any other suitable device. In one embodiment, pressurized oil is released from the accumulator array so as to maintain a constant pressure differential across the motor 90. This enables steady constant output power to be provided. The control system 82 is operative to control the various elements of the ESRS including the pump 86, the flow of oil into and out of the individual accumulator tanks in the accumulator array 88, and the motor 90 such that the motor delivers substantially constant output power. The output power delivered by the motor can be varied via the control system in accordance with the particular energy demand at any point in time.

A block diagram illustrating a second example embodiment of the energy storage and regeneration system of the present invention is shown in FIG. 5. The ESRS, generally referenced 100, comprises a hydraulic pump 104 coupled to an energy source 102, accumulator array 106, pressure regulator 110, hydraulic motor 114 coupled to a load 116, hydraulic fluid reservoir 120, and control system 122.

As in the first embodiment, variable, irregular input power 102 is converted by the motor to pressurized oil which is stored in the accumulator array 106. In this second embodiment, high pressure 108 from the accumulator array is released in a controlled manner via the control system to the pressure regulator 110. The pressure regulator generates a constant pressure 112 at its output which is used to drive motor 114 which powers the load 116. The oil output of the motor is at substantially ambient pressure 118 and collects in the reservoir 120 where it is fed to the pump 104 to complete the cycle.

A block diagram illustrating a third example embodiment of the energy storage and regeneration system of the present invention is shown in FIG. 6. For illustration purposes only, this embodiment uses the ESRS in an electricity generating application. It is appreciated that the mechanical energy output by the system can be used in any desired fashion depending on the particular application and is not limited to the electricity application described herein.

The ESRS, generally referenced 130, comprises pump 134 coupled to an energy source 132, accumulator array 136, one or more power units 138, electric power control block 146, control system 152, and optional hydraulic fluid reservoir 154. The M power units 138 (where M is a positive integer) are connected sequentially in tandem with each unit comprising a hydraulic motor 140, and a floating accumulator 144. The motor 140 is coupled to an electric generator 142 for converting the mechanical energy generated by the motor into electrical energy. The outputs of the M generators are input to an electric power control circuit 146 which combines and regulates the electricity from the generators to produce electric output power 156 which is supplied to a utility or directly to end users.

Note that the energy source 132 may comprise any available source of energy, e.g., wind, solar PV or thermal, hydro, geothermal, electrical, etc. Ultimately, it is converted to mechanical energy to turn the shaft of the hydraulic pump 134. Therefore, depending on the energy source, energy conversion may be required. For example, consider a PV solar energy source. The electricity generated is first input to an electric motor whose mechanical output is then coupled to the shaft of the hydraulic pump.

The floating accumulator in each power unit is configured and controlled so as to maintain a substantially constant pressure differential (or delta P) across it's respective motor. Providing a constant pressure differential across each of the motors allows the system to generate steady, constant output power. The pressures in the different floating accumulators are constantly being adjusted so that the pressure drop across the motors is maintained at a substantially constant level. Note that the M^(th) power unit does not have a floating accumulator as there is no motor in a downstream power unit that requires pressure regulation. The oil output of the motor in the last power unit returns to the optional reservoir 154 or is cycled directly back to the pump 134.

Note that there is at least one floating accumulator 144 in the system 130 connected serially to hydraulic motor 140 and arranged to control the pressure across a respective motor. This is achieved by storing pressurized hydraulic fluid output from the motor. Increasing the pressure in the floating accumulator causes the pressure drop across the motor to decrease. On the other hand, lowering the pressure in the floating accumulator causes the pressure drop across the motor to increase. In this manner, the pressure drop across the motor can be kept fairly constant. Using floating accumulators allows adjusting the pressure level across each motor to provide a desired power to the load, and also to minimize heat loss and waste of hydraulic pressure across the motors. Additionally, determining the hydraulic pressure across hydraulic motors 140 allows controlling the provided output power.

Note also that the floating accumulators 144 may comprise floating accumulator clusters arranged to temporarily store a particular amount of pressurized hydraulic fluid. After storing the pressurized hydraulic fluid, floating accumulators 144 (1) set the back pressure across its upstream motor, and (2) provide their stored power to downstream hydraulic motors in accordance with control outputs generated by control system 152.

In one embodiment, the ESRS is configured to maintain variable pressure levels in the accumulator tanks via the control valves arranged to regulate the pressure level in each respective accumulator tank. Separate control over each accumulator tank allows the system to attain a high pressure level with a relatively small amount of hydraulic fluid. The valves are controlled by the control system over one or more communication signal links.

Thus, power from the irregular energy input source 132 is separated from the generation of controlled, steady output power 156 by the storage of hydraulic energy. For example, power storage may take place during the night and power generation during the day.

The control system is configured to receive signals from a plurality of sensors in the system (not shown for clarity). The sensors measure pressures in various parts of the system including, for example, the accumulators, floating accumulators, input and output manifolds, across the motors, pump input and output, etc. The control system is also configured to generate the control signals (e.g., electric, mechanical, pneumatic, hydraulic, etc.) that control the valves, actuators, pumps, motors, etc. in the system. One or more algorithms performed by control system are operative to receive sensor data, user commends, etc. and based thereon to generate the necessary output control signals to maintain a substantially constant pressure differential across the motors in each of the power units.

A diagram illustrating an example accumulator array in more detail is shown in FIG. 7. In one embodiment, the accumulator array 220 comprises a plurality of N individual accumulator tanks 222 (where N is a positive integer), each comprising a bladder 224 filled with a gas 226 such as nitrogen, oil 228, and a valve manifold 221 for letting pressurized oil in 223 and out 225 which is controlled via one or more control signals 227 provided by the control system. The inputs 223 of all the individual accumulators are coupled together and connected to the pump. The outputs 225 of all the individual accumulators are coupled together and connected to the motor in the first power unit.

An external tank 230 filled with gas 232, e.g., nitrogen, is connected in parallel to the bladders 224 of the accumulators in the array. Preferably, the volume of the external tank 230 is substantially larger than the size of the bladder in each of the individual accumulators. This functions to greatly increase the dynamic range of pressures each individual accumulator can handle. Note that the use of an external large gas tank 230 is not required but may be used to increase the efficiency of the ESRS.

Note that the gas bladders in the floating accumulators may also be connected to a shared external gas tank in similar fashion to the accumulator tanks of the accumulator array. The large external gas tank 230 may be shared between all or a portion of the accumulator tanks and floating accumulator tanks. In an alternative embodiment, the floating accumulators may share their own external gas tank (not shown) separate from external gas tank 230.

Each accumulator tank (including the floating accumulator tanks) comprises at least five parts: (1) container, (2) gas (e.g., nitrogen) bladder, (3) piston, (4) input valve, and (5) output valve. In order to maximize the energy stored by the nitrogen it is pre-pressurized to the working pressure of the hydraulic motor, this way all the oil contained in the accumulator can run the hydraulic motor. All energy storage is contained in the gas when the oil, as uncompressible media, presses the nitrogen bladder to its maximum pressure.

Since nitrogen above 33 bar cannot be treated as an ideal gas, one must use the nitrogen thermodynamic properties at each state in the accumulator in accordance with Table 1 below.

TABLE 1 Nitrogen gas thermodynamic properties (from the Nitrogen Database). Pressure, [bar] 100 500 Temperature, [deg C.] 27 41 phase: Supercritical Liquid, SL SL SL Density, [kg/m{circumflex over ( )}3] 111.7 395.2 Specific heat Cp, [KJ/(kg K)] 0.03347 0.03786 Specific heat Cv, [KJ/(kg K)] 0.02179 0.02362 Entropy J/(mol K) 151.8 136.7 Entropy KJ/(Kg K), s 5.42 4.88 Enthalpy, [kJ/mol] 8.183 8.185 Enthalpy, [kJ/Kg], h 297.11 292.18 internal energy, [kJ/mol] 202.6 165.7 internal energy, [kJ/Kg], u 7,232.25 5,915.03

As an example, consider the pre-pressurized state to be 100 bar and the pressure in the accumulator when full is 500 bar. In an initial state i, the entire accumulator tank is filled with gas at 100 bar and 27° C. (see FIG. 2) In a final state f the accumulator tank contains oil and compressed gas, with the same weight, at 500 bar and 41° C. (see FIG. 3).

Knowing the initial conditions of the gas defines the gas mass that does not change the entire process. From the first law of thermodynamics, the work done by the oil on the gas can be calculated.

ΔU=Q+W  (1)

Where ΔU is the change in internal energy, Q is the heat exchanged with the gas, and W is the work done by the oil on the gas.

Designing the accumulator tank in a way whereby minimal heat is exchanged between the gas and its boarders will define the stored energy, i.e. work W, as the change in internal energy where Q=ΔH=0. Knowing the final state where gas is compressed to the highest pressure, the volume the gas takes up is defined and the amount of oil contained in the accumulator can be calculated.

A block diagram illustrating a fourth example embodiment of the energy storage and regeneration system of the present invention is shown in FIGS. 8A and 8B. The ESRS, generally referenced 160, comprises a hydraulic pump 172, accumulator array 162, one or more power units 174 arranged sequentially one after the other, a selector 198, and control system 196. Each of the power units 1 through M comprises a proportional valve, hydraulic motor 178, generator 180 (for electricity generation application), hydraulic selector 184, floating accumulator 188 and controlled manifold 186. Note that the last power unit in the chain (i.e. the M^(th) unit) does not have a selector or a floating accumulator since these are not needed as it is not connected to any further downstream power units.

As in the embodiment described supra, the variable input power 206 generated by the energy source 204, e.g., wind, solar, hydro, etc. is coupled to the shaft 208 of the pump 172. The pressurized fluid output of the pump is directed to the accumulator array 162. The accumulator array, described in more detail in connection with FIG. 7, comprises a plurality of individual accumulators 1 through N. Each having a control manifold 166 at one end. Both input 170 and output 168 valves are used to control fluid entering and exiting each accumulator. When the input energy source is available, the control system controls the manifolds on the accumulator such that fluid is allowed to enter one or more of the individual accumulators. The internal pressures of all the tanks in the accumulator array is constantly monitored by the control system. Based on other sensor readings, the system state and desired power output, the control system generates the appropriate control signals to optimally maintain the pressure in each tank in the array.

When stored hydraulic energy is to be released and converted into mechanical (or electrical energy, for example), the control system opens one or more output valves 168 on the tanks in the array. The released pressured fluid is directed to power unit 1. The fluid enters a proportional valve 176.

A proportioning valve is a valve that supplies a reduced pressure to an output line. Proportional valves are used to vary either flow or pressure to reduce lunge and shock. The solenoids on these valves shift the spool more or less. According to the voltage applied to proportional solenoids, they can change the speed at which the spool shifts or the distance that it travels. Because the spool in a proportional valve does not shift all the way, all at once, the valves control the acceleration and deceleration of an actuator. Usually, varying shifting time of the spool controls acceleration and deceleration. Varying voltage to the coil limits spool travel to control the maximum speed of an actuator. The control system generates the appropriate variable electric signals.

The output of the proportional valve is input to the motor 178. The motor produces useful mechanical work, e.g., to drive a generator 180 to produce electric output power 182. The output of the motor is input to a selector 184 which can steer fluid to selector 198 for return to the pump 172 or to the input valve 190 of manifold 186, in accordance with a control signal 194. The manifold 186 is connected to the floating accumulator 188. The output valve 192 feeds the proportional valve in the downstream power unit. One or more control signals 167 from the control system 196 control the opening and closing of the input and output valves as well as the proportional valve and selector components.

Note that the selectors may switch the oil flow completely between the two outputs or are variable in that a different proportion of oil may be directed to both outputs simultaneously, 25% to port A, 75% to port B.

The function of the floating accumulator is to aid in maintaining a constant pressure drop across each of the motors in the chain of power units. The input and output valves of the manifold connected to each floating accumulator are manipulated and controlled along with the release of hydraulic energy from the accumulator array to maintain a substantially constant pressure drop across each motor. A constant pressure drop across each motor is desirable in order to maintain a fairly constant output power. In this fashion, a variable, sporadic input energy source is converted to steady output power by converting the input energy into hydraulic energy, storing this hydraulic energy in the accumulator array and the floating accumulators, and converting the stored energy to mechanical or electrical energy on a steady, constant basis in accordance with user or customer demand.

A description of the full circuit path the oil takes will now be provided starting with the energy entering the system. Energy from a source 204 enters the ESRS as motion (i.e. rotation). The source can be, for example, a windmill or electrical motor based on a solar field or electrical net. The motion entering the system is coupled to the shaft 208 of a hydraulic pump which is operative to press the oil fed to the pump into different pressures. The hydraulic pump raises the oil pressure and the high pressure oil is stored in the accumulator array according to the control system control signals. The signals are generated by one or more algorithms tailored to the particular energy scenario, e.g., wind, solar, sea waves, etc. In case of a wind turbine, for example, the energy, in motion form, is probably not uniform or constant. Energy from a solar panel field enters via an electrical motor and energy from waves likely enters as hydraulic energy in the form of pressurized oil. As described supra, the control system receives data, e.g., sensor, external data, feedback signals, etc., and in response sends instruction to the various components connected to it. For example, the control system sends a control signal to each accumulator in the array as well as the floating accumulators in the power units to either accept or discharge oil via the electric valves that connect the accumulators to an oil manifold. A pressure sensor is connected to each accumulator that sends a signal with the pressure to the control system. If the pressure is not at the highest level possible, i.e. the accumulator is not full, the control system directs oil to that accumulator. A similar method applies for discharging the accumulators. The control system will direct an accumulator to discharge its oil if it is full or has sufficient pressure for the particular needs at that point in time.

When all accumulators are full or when the control system determines that energy should be released, the control system opens the release valve associated with a specific accumulator, and high pressure oil is sent to the hydraulic motor in power unit 1 that rotates the generator to generate electricity.

Note that the control system is suitably programed to discharge oil in accordance with the demand for electricity generation. This demand can be influenced by price, i.e. the particular tariff in place at the time, or by a shortage of electricity. Another criterion considered by the control system is the availability of energy coming into the system. For example, if the system is fully loaded, i.e. all accumulators are full, the system discharges oil and generates electricity even at a low tariff but maintains the accumulators in a full state in the event the input energy drops or ceases completely and/or the tariff increases, i.e. the sale of electricity is more profitable.

This process takes place in parallel with all accumulators, i.e. array and floating, in the system. The charging and discharging of all accumulator is under the supervision and control of the control system. The accumulators in the system (array and floating) are connected to a manifold with different valves for charging and discharging. When one or more accumulators are discharging, the other accumulators can be charging since the oil discharge path is separate from the oil charge path.

The oil exiting the hydraulic motor enters the floating accumulator via its corresponding selector to create a back load (i.e. back pressure) so only the desired pressure drop occurs across the motor and to enable the generation of electricity via the generator. If the electric power generated is sufficient for the particular demand, then there is no need to operate additional hydraulic motors in downstream power units. In this case, the pressurized oil is discharged back to the hydraulic pump via selector(s) 198 installed along the discharge path 197. Note that all selectors in the system are controlled by the control system 196.

A cycle ends when pressurized oil reaches the pump either to raise its pressure and store energy or to enter an accumulator tank to be stored with the same pressure from the discharge path if there is no input energy supplied to the system at that point in time. Note that all pressurized oil movement is controlled by the control system 196 via the selectors and electrical valves that open and close the accumulator tanks.

The control system is operative to input a plurality of control input signals 202 from various sensing devices in the ESRS (not shown for clarity), such as pressure sensors, flow sensors, position sensors, switches, potentiometers, photoelectrics, digital encoders, strain gauges, thermocouples, accelerometers, microelectromechanical systems (MEMS), gauges, etc. In addition, the control system is operative to generate a plurality of control output signals 200 for controlling the active components in the system, such as input and output valves, proportional valves, selectors, linear and nonlinear actuators, cylinders, pumps, ac and dc motors, voice coils, servo motors, hydraulics, pneumatics, etc.

A block diagram illustrating a fifth example embodiment of the energy storage and regeneration system of the present invention is shown in FIGS. 9A and 9B. In this example embodiment, the ESRS, generally referenced 210, is constructed similarly to that of system 160 shown in FIGS. 8A and 8B. The difference is that system 210 includes an oil reservoir 212 for storing hydraulic oil at ambient pressure. The reservoir is fed from an output of the selector 198 which is fed from the output of the motor in power unit M and the outputs of the selectors in power units 1 through M−1. Otherwise, operation of ESRS 210 is similar to that of ESRS 160.

A diagram illustrating an example control system of the present invention in more detail is shown in FIG. 10. The control system, generally referenced 240, comprises a processor 242, digital/analog control circuit block 244, user interface block 246, input signal conditioning/interfacing block 248, software control algorithms block 250, and output signal conditioning/interfacing block 252. The processor 242 is connected to the various blocks of the control system over one or more control/data buses 258.

The processor 242 may comprise any suitable processor such as a multiprocessor system, microprocessor, microcontroller or microcomputer based system, programmable logic controller (PLC), single board computer (SBC), ASIC or FPGA core, DSP core, distributed computing environment, etc. capable of running the control algorithms, sequencing and timing logic, etc. of the ESRS. Although not shown, the control system comprises any necessary volatile and non-volatile memory to operation purposes including storing of program code.

In one embodiment, the user interface 246 is coupled to a display 260 and one or more input/output devices 262 such as a keyboard, mouse, printer, external memory, etc. The input signal conditioning/interfacing block 248 is operative to receive a plurality of sensor data signals from the various sensors, switches, encoders, etc. in the ESRS. The circuitry in block 248 provides the required conditioning circuitry, analog to digital converters (ADCs), filters, discrete circuits, sense amplifiers, amplifiers, and other circuits to convert the input sensor data 256 into digital signals that can be used by the digital algorithms. The circuitry in block 252 provides the required conditioning circuit, digital to analog converters (DACs), amplifiers, pulse width modulation (PWM) circuits, power transistors, op amps, and other circuits to convert the actuator data output by the processor and/or the digital/analog control circuit block 244 to actuator data signals 254 that are used to operate the various valves, motors, pneumatics, cylinders, actuators, etc. in the ESRS.

A flow diagram illustrating an example method of generating and storing hydraulic energy is shown in FIG. 11. As described supra, the ESRS receives potentially variable, non-constant input power from an energy source such as wind, solar, etc. (step 420). The ESRS is operative to convert the variable, non-constant input power received into mechanical energy (step 422). For example, electric power from a PV solar array is fed to a generator to convert the electric energy into mechanical energy. The mechanical energy is then coupled to the shaft of the hydraulic pump (step 424). Note that a plurality of hydraulic pumps may be used depending on the particular application and amount of input power to be handled.

The control system, based on sensor readings, determines one or more accumulator tanks in the accumulator array to steer the pressured oil to generated by the pump (step 426). The control system generates the appropriate control signals (e.g., valve control signals) to open the input valves on the one or more accumulator tanks to receive the pressurized oil (step 428). At some point later in time, the control system generates the appropriate control signals to close the input valves on one or more accumulator tanks if they become full or if the input power falls off below a particular threshold (step 430).

A flow diagram illustrating an example method of generating steady electric/mechanical energy from stored hydraulic energy is shown in FIG. 12. First, the desired output power to generate is determined (step 440). This is based on the particular energy demand of the load connected to the ESRS. Typically, this demand is dynamic and thus the control system is constantly making adjustments based on the demand at any point in time.

Based on the desired power, the number of power unit(s) to deploy is determined (step 442). Depending on the particular implementation of the invention, each power unit is capable of generating a certain amount of power. The demand at any point in time translates to a minimum number of power units required.

Once the number of power unit(s) is determined, based on sensor readings, the control system determines which one or more accumulator tanks in the accumulator array to open (step 444). To drive the power unit(s), the hydraulic energy stored in one or more accumulator tanks must be released. The control system generates the appropriate control signals to open the one or more accumulator tanks (step 445).

The control system then generates appropriate initial values for the control signals to the proportional valves, selectors, and floating accumulators in each of the deployed power unit(s) (step 446). Based on sensor readings, the control system monitors the pressure drop across the motors in each deployed power unit (step 448).

The control unit, in response, controls the input and output valves of each floating accumulator to maintain a near constant desired pressure drop across each motor (step 450). As accumulator tanks deplete their stored hydraulic energy (i.e. pressured oil), the control system steers newly generated hydraulic energy from the input energy source to the empty accumulator tanks and configures other accumulator tanks to send their stored hydraulic energy to the power unit(s) (step 452).

It is noted that the methods of FIGS. 11 and 12 are performed in parallel, whereby the accumulator tanks in the array are constantly monitored. Hydraulic energy generated from the input energy source is constantly being stored in the array with the control system monitoring the pressure in each tank and steering the generated hydraulic energy accordingly.

At the same time, hydraulic energy is released from the array to keep the power unit(s) generating a constant steady stream of output power. The control system utilizes the floating accumulator in each power unit to aid in maintaining a steady optimal pressure drop across the motor in each power unit. In this manner, a substantially constant level of output power is generated and provided to the load.

Those skilled in the art will recognize that the boundaries between logic and circuit blocks are merely illustrative and that alternative embodiments may merge logic blocks or circuit elements or impose an alternate decomposition of functionality upon various logic blocks or circuit elements. Thus, it is to be understood that the architectures depicted herein are merely exemplary, and that in fact many other architectures may be implemented which achieve the same functionality.

Any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality may be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermediary components. Likewise, any two components so associated can also be viewed as being “operably connected,” or “operably coupled,” to each other to achieve the desired functionality.

Furthermore, those skilled in the art will recognize that boundaries between the above described operations merely illustrative. The multiple operations may be combined into a single operation, a single operation may be distributed in additional operations and operations may be executed at least partially overlapping in time. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be altered in various other embodiments.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an.” The same holds true for the use of definite articles. Unless stated otherwise, terms such as “first,” “second,” etc. are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. As numerous modifications and changes will readily occur to those skilled in the art, it is intended that the invention not be limited to the limited number of embodiments described herein. Accordingly, it will be appreciated that all suitable variations, modifications and equivalents may be resorted to, falling within the spirit and scope of the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. 

What is claimed is:
 1. An apparatus for storing and regenerating energy, comprising: a hydraulic pump coupled to a source of mechanical energy providing variable, non-constant input power, said hydraulic pump operative to convert said mechanical energy to hydraulic energy at its output; an accumulator array including a plurality of N accumulator tanks, said accumulator array coupled to the output of said hydraulic pump, said accumulator array operative to store the hydraulic energy generated by said hydraulic pump in one or more accumulator tanks; one or more power units coupled to said accumulator array and operative to convert hydraulic energy released from said accumulator array into mechanical energy; and a control system coupled to said accumulator array and said one or more power units, said control system operative to coordinate the storage and release of hydraulic energy into and out of the N individual accumulator tanks of said accumulator array in accordance with an external power demand such that the variable, non-constant input power is converted into relatively steady, constant power output by said one or more power units.
 2. The apparatus according to claim 1, wherein gas bladders in said accumulator tanks are coupled in parallel to an external gas tank.
 3. The apparatus according to claim 1, wherein each power unit comprises a hydraulic motor.
 4. The apparatus according to claim 1 wherein each power unit comprises a pressure regulator.
 5. The apparatus according to claim 1, wherein each power unit comprises a generator operative to convert mechanical energy into electrical energy.
 6. The apparatus according to claim 1, further comprising a hydraulic fluid reservoir coupled between said one or more power units and said hydraulic pump.
 7. The apparatus according to claim 1, wherein each accumulator tank is capable of operating independently and in isolation to all other accumulator tanks and wherein the pressures maintained in said accumulator tanks are independent of each other.
 8. A method of storing and regenerating energy, the method comprising: receiving variable, non-constant input power from an energy source; converting the input power to hydraulic energy; storing the hydraulic energy generated in a plurality of N accumulator tanks making up an accumulator array; releasing stored hydraulic energy from said accumulator array in a controlled manner to power one or more power units; converting, at each power unit, hydraulic energy released from the accumulator array into mechanical energy; and coordinating, via a control system, the storage and release of hydraulic energy into and out of the N individual accumulator tanks of said accumulator array in accordance with an external power demand such that the variable, non-constant input power is converted into relatively steady, constant power output by said one or more power units.
 9. The method according to claim 8, wherein gas bladders in said accumulator tanks are coupled in parallel to an external gas tank.
 10. The method according to claim 8, wherein each power unit comprises: a hydraulic motor; and a generator operative to convert mechanical energy into electrical energy.
 11. The method according to claim 8, wherein each power unit comprises a pressure regulator.
 12. The method according to claim 8, wherein each accumulator tank is capable of operating independently and in isolation to all other accumulator tanks and wherein the pressures maintained in said accumulator tanks are independent of each other.
 13. An apparatus for storing and regenerating energy, comprising: a hydraulic pump coupled to a source of mechanical energy providing variable, non-constant input power, said hydraulic pump operative to convert said mechanical energy to hydraulic energy at its output; an accumulator array including a plurality of N accumulator tanks, said accumulator array coupled to the output of said hydraulic pump, said accumulator array operative to store the hydraulic energy generated by said hydraulic pump in one or more accumulator tanks; one or more power units coupled to said accumulator array and operative to convert hydraulic energy released from said accumulator array into mechanical energy, each power unit including a hydraulic motor and a floating accumulator; a control system coupled to said accumulator array and said one or more power units, said control system operative to coordinate the storage and release of hydraulic energy into and out of the N individual accumulator tanks of said accumulator array and the floating accumulator in each power unit in accordance with an external power demand such that the variable, non-constant input power is converted into relatively steady, constant power output by said one or more power units; and wherein said control system is operative to control the charging and discharging of pressurized hydraulic fluid into and out of the floating accumulator in each respective power unit such that the pressure differential across a power unit's corresponding hydraulic motor is maintained substantially constant.
 14. The apparatus according to claim 13, wherein gas bladders in said accumulator tanks are coupled in parallel to an external gas tank.
 15. The apparatus according to claim 13, wherein each power unit comprises a generator operative to convert mechanical energy into electrical energy.
 16. The apparatus according to claim 13, further comprising a hydraulic fluid reservoir coupled between said one or more power units and said hydraulic pump.
 17. The apparatus according to claim 13, wherein each power unit comprises a proportional valve coupled to the input of a respective hydraulic motor.
 18. The apparatus according to claim 13, wherein each power unit comprises a selector coupled to the output of a respective hydraulic motor, floating accumulator and a return line to the hydraulic pump.
 19. The apparatus according to claim 13, wherein each accumulator tank is capable of operating independently and in isolation to all other accumulator tanks and wherein the pressures maintained in said accumulator tanks are independent of each other.
 20. A method of storing and regenerating energy, the method comprising: receiving variable, non-constant input power from an energy source; converting, via a hydraulic pump, the input power to hydraulic energy; storing the hydraulic energy generated in an accumulator array; releasing stored hydraulic energy from said accumulator array in a controlled manner to power one or more power units; converting, via a hydraulic motor in each power unit, hydraulic energy released from the accumulator array into a relatively steady source of mechanical energy; providing a floating accumulator in each power unit coupled to a respective hydraulic motor; coordinating, via a control system, the storage and release of hydraulic energy into and out of said accumulator array and the floating accumulator in each power unit in accordance with an external power demand such that the variable, non-constant input power is converted into relatively steady, constant power output by said one or more power units; and control, via the control system, the charging and discharging of pressurized hydraulic fluid into and out of the floating accumulator in each respective power unit so as to maintain a substantially constant pressure differential across a power unit's respective hydraulic motor.
 21. The method according to claim 20, wherein said accumulator array comprises a plurality of individual accumulator tanks, wherein the gas bladders in the accumulator tanks are coupled in parallel to an external gas tank.
 22. The method according to claim 20, wherein each power unit comprises a generator operative to convert mechanical energy into electrical energy.
 23. The method according to claim 20, further comprising providing a hydraulic fluid reservoir coupled between said one or more power units and said hydraulic pump.
 24. The method according to claim 20, wherein said accumulator array comprises N individual accumulator tanks, wherein each accumulator tank is capable of operating independently and in isolation to all other accumulator tanks and wherein the pressures maintained in said accumulator tanks are independent of each other. 